#!/bin/sh

print_usage()
{
    echo "$(basename $0) -- Convert multiple compressed gzip files to bzip2."
    echo "Usage: $(basename $0) [FILES]"
}

if [ $# = 0 ]; then
    print_usage
    exit 1
fi

while [ $# -ne 0 ]; do
    ORIG_GZIPPED_FILENAME=${1}

    # Checking if input file exist.
    if [ ! -f $1 ]; then
	echo "$0: File ${ORIG_GZIPPED_FILENAME} not found."
	exit 1
    fi

    # Checking if input file is a valid gzipped file.
    gzip -t ${ORIG_GZIPPED_FILENAME}
    if [ $? -ne 0 ] ; then
	echo "$0: File ${ORIG_GZIPPED_FILENAME} is not a valid gzip file."
	exit 1
    fi

    # Obtaining uncompressed name of file
    FILENAME=$(gunzip -l ${ORIG_GZIPPED_FILENAME} | sed '1d' | sed 's/\(.*\)% \(.*\)/\2/')
    
    # Decompressing file to standard output and piping result to bzip2
    gunzip ${ORIG_GZIPPED_FILENAME} --stdout | bzip2 --best > ${FILENAME}.bz2
    if [ $? -ne 0 ] ; then
	echo "$0: Error converting file ${ORIG_GZIPPED_FILENAME} to bzip2."
	exit 1
    fi

    # Keeping the original file's timestamp
    touch --reference=${ORIG_GZIPPED_FILENAME} ${FILENAME}.bz2

    # Deleting original .gz file
    if [ -f ${FILENAME}.bz2 ]; then
	rm ${ORIG_GZIPPED_FILENAME}
    fi
    
    shift
done